blob: 477a041a41cfa4601cb796ddf14df3dfcdbde562 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * Copyright (C) 2001 Sistina Software (UK) Limited
3 *
4 * This file is released under the GPL.
5 */
6
7#include "dm.h"
8
9#include <linux/module.h>
10#include <linux/init.h>
11#include <linux/kmod.h>
12#include <linux/bio.h>
13#include <linux/slab.h>
14
Alasdair G Kergon72d94862006-06-26 00:27:35 -070015#define DM_MSG_PREFIX "target"
16
Linus Torvalds1da177e2005-04-16 15:20:36 -070017struct tt_internal {
18 struct target_type tt;
19
20 struct list_head list;
21 long use;
22};
23
24static LIST_HEAD(_targets);
25static DECLARE_RWSEM(_lock);
26
27#define DM_MOD_NAME_SIZE 32
28
29static inline struct tt_internal *__find_target_type(const char *name)
30{
31 struct tt_internal *ti;
32
33 list_for_each_entry (ti, &_targets, list)
34 if (!strcmp(name, ti->tt.name))
35 return ti;
36
37 return NULL;
38}
39
40static struct tt_internal *get_target_type(const char *name)
41{
42 struct tt_internal *ti;
43
44 down_read(&_lock);
45
46 ti = __find_target_type(name);
47 if (ti) {
48 if ((ti->use == 0) && !try_module_get(ti->tt.module))
49 ti = NULL;
50 else
51 ti->use++;
52 }
53
54 up_read(&_lock);
55 return ti;
56}
57
58static void load_module(const char *name)
59{
60 request_module("dm-%s", name);
61}
62
63struct target_type *dm_get_target_type(const char *name)
64{
65 struct tt_internal *ti = get_target_type(name);
66
67 if (!ti) {
68 load_module(name);
69 ti = get_target_type(name);
70 }
71
72 return ti ? &ti->tt : NULL;
73}
74
75void dm_put_target_type(struct target_type *t)
76{
77 struct tt_internal *ti = (struct tt_internal *) t;
78
79 down_read(&_lock);
80 if (--ti->use == 0)
81 module_put(ti->tt.module);
82
Eric Sesterhenn543cb2a2006-04-01 01:08:12 +020083 BUG_ON(ti->use < 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -070084 up_read(&_lock);
85
86 return;
87}
88
89static struct tt_internal *alloc_target(struct target_type *t)
90{
91 struct tt_internal *ti = kmalloc(sizeof(*ti), GFP_KERNEL);
92
93 if (ti) {
94 memset(ti, 0, sizeof(*ti));
95 ti->tt = *t;
96 }
97
98 return ti;
99}
100
101
102int dm_target_iterate(void (*iter_func)(struct target_type *tt,
103 void *param), void *param)
104{
105 struct tt_internal *ti;
106
107 down_read(&_lock);
108 list_for_each_entry (ti, &_targets, list)
109 iter_func(&ti->tt, param);
110 up_read(&_lock);
111
112 return 0;
113}
114
115int dm_register_target(struct target_type *t)
116{
117 int rv = 0;
118 struct tt_internal *ti = alloc_target(t);
119
120 if (!ti)
121 return -ENOMEM;
122
123 down_write(&_lock);
124 if (__find_target_type(t->name))
125 rv = -EEXIST;
126 else
127 list_add(&ti->list, &_targets);
128
129 up_write(&_lock);
130 if (rv)
131 kfree(ti);
132 return rv;
133}
134
135int dm_unregister_target(struct target_type *t)
136{
137 struct tt_internal *ti;
138
139 down_write(&_lock);
140 if (!(ti = __find_target_type(t->name))) {
141 up_write(&_lock);
142 return -EINVAL;
143 }
144
145 if (ti->use) {
146 up_write(&_lock);
147 return -ETXTBSY;
148 }
149
150 list_del(&ti->list);
151 kfree(ti);
152
153 up_write(&_lock);
154 return 0;
155}
156
157/*
158 * io-err: always fails an io, useful for bringing
159 * up LVs that have holes in them.
160 */
161static int io_err_ctr(struct dm_target *ti, unsigned int argc, char **args)
162{
163 return 0;
164}
165
166static void io_err_dtr(struct dm_target *ti)
167{
168 /* empty */
169}
170
171static int io_err_map(struct dm_target *ti, struct bio *bio,
172 union map_info *map_context)
173{
174 return -EIO;
175}
176
177static struct target_type error_target = {
178 .name = "error",
179 .version = {1, 0, 1},
180 .ctr = io_err_ctr,
181 .dtr = io_err_dtr,
182 .map = io_err_map,
183};
184
185int __init dm_target_init(void)
186{
187 return dm_register_target(&error_target);
188}
189
190void dm_target_exit(void)
191{
192 if (dm_unregister_target(&error_target))
193 DMWARN("error target unregistration failed");
194}
195
196EXPORT_SYMBOL(dm_register_target);
197EXPORT_SYMBOL(dm_unregister_target);